This invention relates generally to an ink ribbon cartridge for use in a recording device, and more specifically to an ink ribbon cartridge including a one piece clutch mechanism used with a drive gear.
In a thermal ink ribbon cartridge, an ink ribbon is wound around a supply tube and extends to a take-up tube. An ink layer is formed on one surface of the ink ribbon. A spindle without a gear is provided at one end of each of the supply tube and the take-up tube while a spindle with a gear is provided at the other end of the supply tube and take-up tube. The spindles are selectively removable from the tubes.
At the time of ink ribbon replacement, each of the spindles is removed from a snap fit engagement with a corresponding hole in the housing of the ink ribbon cartridge. Then, the spindles are removed from their corresponding ends of the supply and take-up tubes. Replacement tubes with ink ribbon are installed onto the take-up and supply spindles and are attached to the ink ribbon cartridge housing. Subsequently, the ink ribbon cartridge is mounted in a printer or facsimile system. If the ink ribbon is improperly mounted or the direction of winding is reversed from the proper direction, the ink ribbon cannot be wound up thus resulting in a failure in printing.
Existing cartridges use a clutching mechanism for an ink ribbon take-up tube which has three separate components, an insert, a hub and a drive gear. As seen in FIG. 1A, a take-up tube 10 has an opening 12 extending therethrough and one or two slots 14 in each end of the tube. Tube 10, which is made of cardboard, has a plastic insert 20 which is inserted into one end of the tube and has tabs (not shown) which engage the slots 14 and snap the insert into place within the tube opening. The insert then remains as part of the take-up tube. The insert has a lip 22 which engages an end surface of the cardboard tube. The insert has an opening 24 extending therethrough. Referring to FIG. 1B, at an end 26 of the insert, which is opposite the end with lip 22 are a series of drive surfaces 28 and slip surfaces 30 formed by angled slots 32 equally spaced apart along a peripheral edge of the insert. The drive and slip surfaces extend axially inwardly from end surface 26 of the insert 20. The drive surfaces are substantially radial edges which form an abutment shoulder for drivingly engaging a drive gear. The slip surfaces have smooth, tapered surfaces or slopes which have a chord component which allows a drive lug to slip along the surfaces.
A hub 40 is snap fit onto a drive gear assembly 50. The hub has several prongs 42 which extend axially from a flat disk surface 44 and extend into matching slots 52 in the drive gear. The prongs are then locked into place within the gear and attach the hub to the gear. The hub further comprises a central portion 46 having an opening 47 therethrough and an end portion 48 with a slot 49 therethrough. The gear assembly includes an elongated leg portion 54 which extends through the opening in the central portion of the hub. Portion 54 includes a cantilever member 56 which is formed between grooves in the portion. The cantilever member has a drive lug 58 which extends through opening 47 of the hub and protrudes through slot 49. The drive lug is formed of a resilient material and can be depressed radially inwardly toward a center of the hub as the hub and drive gear are installed together. Once the drive lug is fully received in the hub, it extends radially outwardly through the slot of the hub and is locked within the slot.
The drive gear and hub assembly are then inserted into the plastic insert 20 in the cardboard tube. The drive lug is again depressed radially inwardly as the hub is axially inserted through an opening 24 in the insert 20 until the lug reaches the drive and slip surfaces at the end of the insert. The lug is depressed inwardly by the slip surfaces 30 and does not allow the drive gear to rotate the cardboard tube. That is, the drive lug allows the drive gear and hub to rotate counter-clockwise (see FIG. 1B) with respect to the slip surfaces and does not engage or lock to the insert. The drive gear and hub do not rotate the cardboard tube. However, if the hub and drive gear are rotated in the opposite direction, i.e. clockwise, the drive lug extends through one of the slots of the insert and engages one of the drive surfaces 28 thus providing a positive drive and rotating the insert and the cardboard tube in a clockwise manner along section AA. Thus, cardboard tube 10 can only rotate in one direction as driven by the drive gear.
A problem with this existing design is that the end of the cardboard tube with the plastic insert can only accommodate the drive gear with the hub and drive lug. This end is not compatible with any of the other spindles, i.e., the supply spindles or the other drive gear arrangements.
Thus, a one piece clutch mechanism which accomplishes the same function of permitting rotation of the take-up spool in only one direction would be desirable. This clutch mechanism would allow the end of the cardboard tube to be compatible with other drive gears and other spindles. Furthermore, no separate insert would be required within the cardboard tube. Accordingly, it is desirable to provide a new and improved ink ribbon cartridge which would meet the above stated needs and others and provide better, more advantageous results.
Generally speaking, the present invention relates to an ink ribbon cartridge which uses a drive gear that prevents improper winding of the take-up spool and thus preventing failure in printing.
More particularly, the invention relates to an ink ribbon cartridge with a one piece clutch mechanism which is inserted into a drive slot of a take-up tube. The take-up tube has a pair of slots which provide two surfaces against which a cantilever member of a drive gear contacts and drives the tube and rotate it in one direction. The drive gear cannot rotate the tube when the gear is rotated in the other direction. This is accomplished by including a ramp surface on one end of the cantilever member which is deflected inwardly when pushed against a slot in the take-up tube when rotated in the other direction. The gear rotates but the take-up tube remains stationary. When the gear is rotated in the one direction, the cantilevered member has a flat end which engages the slot within the tube and provides a positive drive when rotated against the tube thus rotating the tube along with the drive gear.
In particular, the present invention relates to an ink ribbon cartridge with an ink ribbon wound about first and second tubes. Spindles are received on each end of each tube. The tubes each have a first and second end with at least one slot formed in each end. The spindles have first and second ends where one of the ends has a disk portion and the other end is received by one of the slots in each tube. The second end of one of the spindles has a cantilevered member which engages a slot of a tube and rotates the tube in only one direction. The cantilevered member elastically deforms upon deflection toward a center of the spindle so that the spindle rotates relative to the stationary tube in the opposite direction.
The cantilevered member has an end having a radial edge and a ramp side adjacent the radial edge. The radial edge is generally parallel to a slot of one of the tubes. Rotation of the spindle in one direction abuts the radial edge against a wall of the slot thus providing a positive drive and allowing rotation of the tube with the spindle. Rotation of the spindle in a second direction opposite to the first direction causes the ramp side to contact and slide along a wall of the slot, thus deflecting the cantilevered member inward toward the center of the spindle. The spindle is rotated and the tube is not rotated when the cantilevered member deflects inwardly.
One advantage of the present invention is the provision of a one piece clutch mechanism for providing a drive gear for rotating a take-up spool in only one direction.
Another advantage of the present invention is the provision of a one piece clutch mechanism which does not have a separate insert to be inserted into one end of a take-up tube thus allowing each end of the tube to receive take-up or supply spindles.
Yet another advantage of the present invention is the provision of a one piece clutch mechanism which minimizes the number of parts and is easy to manufacture.
Still other aspects and advantages of the invention will become apparent to those skilled in the art upon reading and understanding the following detailed description.